Beyond edge injection: area effects in graphene-metal contact resistance

Abstract

Contact resistance between graphene and metal electrodes critically limits device performance, yet the role of contact area versus edge current crowding remains unclear. We designed two device geometries with identical channel dimensions, but different contact areas to isolate area-dependent effects. Using a metal-on-bottom fabrication process, we demonstrate through transmission line method and four-probe measurements that the top-electrode contact device exhibits three to four times lower contact resistance than the top-lead contact device across all gate voltages. This provides the first experimental evidence that contact resistance is governed by distributed charge transfer across the entire interface, not solely by edge injection. Our findings suggest that both Landauer and Bardeen transfer Hamiltonian models are essential for describing graphene-metal contacts, opening new pathways for contact engineering in two-dimensional devices.